I don't think they are added on, I think they are the sides of his shirt, cause in part of the pictures actually taken after they are walking into the ceremony, those are NOT there---and in the closing credits---Heath has his jacket off and is retucking everything with Michelle supervising---then if you look at the pictures--of him and Sean P. he is all tucked in and putting his jacket on in one of them---so I am thinking that the shirt was hanging out when they were going in, but he fixed it just before they went into the actual tent.
there is a video clip link on DC right now that shows them walking---and Michelle doesn't look or move like she has any bumps to me. She looks skinny if anything while she is walking through the crowd into the gate.